Percussive tool



United States Patent James C. Swain Columbus;

David L. Thomas, Columbus; John L. Nagely, Sidney, Ohio May 17, 1968Dec. 15, 1970 Westinghouse Air Brake Company Wilmerding, Pa.

a corporation of Pennsylvania lnventors AppL No. Filed Patented AssigneePERCUSSIVE TOOL 19 Claims, 3 Drawing Figs.

US. Cl. 173/136,

173/139 lnt. Cl B2511 9/00 Field of Search 173/80,

ABSTRACT: A percussive rock drilling device operable by fluid pressureand having a striker element for imparting blows to a drill steel chuck,the striker being provided with cushioning means for absorbing shock inthe event of overtravel and the chuck being supported for reciprocationand rotation on bearings which are protectively isolated outside of adust evacuation zone.

PATENTEDUEUSIQYU 5 7 0 sum 1 0r 2 ([56 array *3 winnin 2; T32 IPERCUSSIVE TOOL BACKGROUND In the drilling of rock and ore, it iscustomary to employ percussive drilling tools which utilize pressurizedfluid for delivering a succession of impact blows to a striking element.In most cases, these devices have heretofore used pneumatic motorsoperable by compressed air as the power. source. However, more recently,it has been proposed to use percussive drills powered by hydraulic fluidunder pressure and acting on a reciprocating piston to motivate thestriker.

In these devices, it has also been proposed to provide means forimparting rotation to the drill steel chuck as the percussive blows aredelivered, such rotation being effected by various means. By way ofexample, one such means for rotating the drill steel chuck duringpercussive operation utilizes a rotary motor powered by pressurizedfluid asis the reciprocating motor. This requires that the drill steelchuck be supported for both reciprocating and rotational movement.

. Since the impact blows imparted to the striker in these drills arenecessarily at high velocity in order to perform the required work,considerable shock is encountered during reciprocation thereof,particularly when the drill steel is running loose or free and thestriker tends to overtravel. Also, as the drill steel performs its work,much dust is conveyed through the area of the drill steel chuck, andthis dust is extremely harmful to the chuck bearings and other operatingparts. In addition, any improper or inaccurate balancing or alignment ofparts leads to excessive wear and costly maintenance.

SUMMARY It is therefore an object of the present invention to provide animproved percussive rock drill for either stoper or horizontal drillingwhich obviates the aforesaid disadvantages and objections attendantprior devices of this general type.

Another object of this invention is to provide a percussive drillingtool which embodies highly effective shock cushioning and snubbing meansfor absorbing and minimizing shock resulting from overtravel of thestriker element.

Still another object of the invention is to provide a fluid actuatedpercussive drill wherein the drill steel chuck is mounted for rotationas well as reciprocation in a highly efficient bearing assemblage whichis effectively protected from dust and other foreign matter.

A further object of the present invention is to provide a fluid actuatedpercussive drill having an annular dust collecting chamber surroundingthe drill steel chuck, the chamber being effectively sealed from thebearings and operating parts of the apparatus and being subjected tosuitable vacuum for evacuating the dust therefrom.

An additional object of the invention is to provide a percussive rockdrill operable by pressurized fluid and having a striker piston assemblywhich is self-centering and which includes a snubber piston cushioned byregulated fluid pressure for absorbing shocks upon overtravel of thestriker piston.

These and other objects and advantages of the invention will becomeapparent from the following detailed description.

THE DRAWINGS A clear conception of the several features constituting thepresent invention and of the mode of constructing and utilizing atypical hydraulic stoper type drill embodying the improvements may behad by referring to the drawings accompanying and forming a part of thisspecification, wherein like reference characters designate the same orsimilar parts in the various views.

FIG. 1 is a transverse vertical section through a typical hydraulicallyoperated stoper drill embodying the invention and showing the strikerpiston in its retracted position;

FIG. 2 is a similar sectional view through the drill but showing thestriker piston advanced to its extended impacting position; and

FIG. 3 is a somewhat enlarged fragmentary sectional view of the valvingarrangement for the snubber piston.

DETAILED DESCRIPTION Referring to the drawings, the improvementsconstituting the present invention are shown therein as embodied in ahydraulically operable rotary-percussive drill of the stoper type suchas fully disclosed in U.S. Pat. No. 3,230,71 1, dated Jan. 25, 1966 toJames C. Swain, et al. and entitled Hydraulic Motor Means. Reference maytherefore be made to such prior patent for a more detailed descriptionof the operation and control of the drill motor and its attendant partsas well as the hydraulic system per se.

Generally, the assemblage shown herein comprises a housing having itsrear or lower portion 8 provided with a bore 12 extending therethrough.Slidably and rotatably confined in the front or upper portion 10 of thehousing in axial alignment with the bore 12 is a chuck l4 carrying'adrill steel 16 having a work performing bit 18. A striker piston 20 ismounted for reciprocatory movement within the bore 12 of the housingportion 8 so that the front end 22 thereof will contact the adjacent endof the drill steel chuck 14 upon movement of the striker 20 in onedirection. Suitable means is also provided for reciprocating the striker20 to impart a succession of blows to the chuck 14 to therebypercussively actuate the same.

As shown and described in detail in the aforesaid US. Pat. No.3,230,711, the means for driving the striker 20 toward and into contactwith the chuck 14 may comprise a hydraulically actuated impact piston 24slidably carried in the bore 26 of a cylindrical housing 28 closing therear end of the bore 12. The impact piston 24 is disposed concentricwith the striker 20 and is actuated by pressurized hydraulicfluidconducted thereto from a suitable supply source via inlet 30 past anaccumulator 32 under the control of a reciprocating spool type valve 34.In operation, the impact piston 24 is accordingly reciprocated and onits forward motion, drive the striker 20 toward the chuck 14, thestriker being returnable after each forward stroke as by means of aspring 36.

Thus, a succession of percussive blows are imparted to the chuck 14 innormal operation, and as long as the drill bit 18 is firmly held againstthe work, the blows delivered by the striker 20 are transmitted by thechuck 14 to drill 16. However, should the drill bit encounter anextremely soft or hollow spot or be permitted to run free, the striker20 will overtravel on its forward stroke, and due to the high velocityof movement, extreme shocks will result along with the possible seriousdamage to the device. One feature of this invention is to provide animproved means for absorbing these shocks and for cushioning the partsduring such abnormal operation.

For this purpose, an annular member 40 is provided, The member 40 beingslidably confined within a sleeve 58 in the bore 12 for independentmovement within predetermined limits as defined by an annular chamber42. The member 40 is in the nature of a hollow piston having acylindrical guide portion 44 and an outwardly extending annular flange46 received within the chamber 42. The chamber 42 is pressurized byhydraulic fluid admitted thereto above or on the forward side of thepiston flange 46 via port 48, annulus 48, and port 48" whichcommunicates with a suitable supply source, not shown, as through a hoseor supply conduit 50. As shown, the striker 20 is provided with anannular flange 52 or similar portion cooperable with the rear of theannular member 40 upon overtravel of the striker, and the impacts of thestriker on its forward stroke are thereby absorbed by the member 40acting as a snubber piston (see FIG. 2). Proper pressure may beconveniently maintained in the chamber 42 and the supply line leadingthereto as through use of a pressure regulator and/or accumulator 54 toprovide for the correct snubbing action and return of the snubber pistonas hereinafter more fully described.

For the purposes of properly centering and guiding the striker 20 andsnubber piston 40 and for additionally cushioning against shocks whilealso permitting the provision of an efficient seal, the stroker, itssnubber piston and its return spring are all housed as a unit in asingle shell or sleeve 58. As shown,

" the sleeve 58 has a cylindrical rear portion 60 of largest diameterreceived in the bore 12 with the annular flange 52 of the striker 20slidable therein, the annular chamber 42 being formed in the forward endof the portion 60 for slidably receiving the flange 46 of the snubberpiston 40. The interjnediate cylindrical portion 62 of the sleeve member58 is of somewhat reduced diameter, and the sleeve portions 60 and 62are joined by an outer annular shoulder or flange 64 which is tapered asshown for seating against a resilient O-ring 66 guided and retainedconcentric within the sleeve. The spring 36 is compressed between theflange 52 of the striker 20 and the inner shoulder 72 formed between theend portion 70 and intermediate portion 62 of the sleeve 58 and therebyacts to return the striker 20 after each forward stroke thereof. Inactual practice, shims 82 are utilized between the flange of housing 28and the adjacent end of housing 8 to firmly seat the housing 28 andsleeve 58, and the O-ring 66 functions both as a'seal and as a resilientmember to cushion shocks transmitted through deflection of the taperedsleeve portion 64 in the event of overtravel. To provide against oilbuildup in the chambers 74, 76 and insure free movement of the striker20 responsive to the action of the impact piston 24 and spring 36, thestriker 20 is provided with ports 78, 80 respectively.

. Eln addition to being mounted for percussive action, the chuck 14 isalso mounted for selective rotary motion within a bore 86 formed in thefront or upper housing portion 10 which is closed by cap 84, the chuckbeing axially aligned with the bore 12, sleeve 58 and striker 20. Asshown, the chuck 14 is formed with a cylindrical body portion 88 ofsomewhat enlarged diameter intermediate the front and rear ends 80, 92respectively. Adjacent the forward end 90, the body portion 88 of thechuck is supported for both reciprocatory and rotary motion in the innerrace of a bearing 94 mounted in the bore 86. The opposite end of thebody portion 88 is slidably received in a cylindrical portion 96 whichis formed in the hub 98 of a gear 100, the adjacent reduced end 92 ofthe chuck having splines 162 received in grooves 104 in the hub 98 forpermitting axial movement of the chuck 14. The chuck 14 is accordinglyfree to move axially within limits defined by the inwardly projectingflange or shoulder 106 at the forward end of the housing 84 and theshoulder 188 formed in the gear hub 98ibetween which the body portion 88is confined.

The gear 100 meshes with a gear 110 which is driven by a suitable fluidmotor 112 under the control of an operator to thereby selectively rotatethe chuck 14 through its spline connection 102, 104, the gear 100 beingmounted for rotation on a bearing 114 having its inner race carried bythe reduced forward portion 70 of the sleeve 58. The hub 98 of gear 100also has a bearing 116 mounted thereon, the outer race of which isseated within a cylindrical portion 118 of the bore 86. Thus, the gear100 and chuck 14 are centered with respect to the sleeve 58, striker 20and bore 86;, and the chuck 14 is rendered freely axially movable withinpredefined limits for percussive action while also being rotatable.

As the bit 18 performs its work during drilling, considerable abrasivedust or cutting fines are created, and the operating parts exposedthereto are subject to extensive abuse unless adequately protected. Inthe present instance, this dust is collected and removed in 'a highlyefficient manner and the bearings and operating parts are maintainedrelatively dust free. This is accomplished by providing an annular spaceor chamber 122 within the bore 86 surrounding the medial body portion 88of the chuck 14 and establishing a low pressure condition in the chamberto evacuate the same. The chamber 122 is placed in communication withthe work by providing axially aligned passageways 124, 126 in the drillsteel 16 and bit 18 respectively, the passageway 124 communicating atits inner end with the annular chamber 122 via one or more passageways128 formed in the chuck. 14. In turn, the annular chamber 122 may beconnected to a suitable source of vacuum through port 130 and tube orhose 132. Dust is thereby drawn through the passageways 124, 126, 128and into the chamber 122 from which the collected dust is evacuatedthrough port 130 and hose 132. v

The bearings 94 and 116 are sealed from the dust collection chamber 122by an annular spacer member 136 spanning the chamber 122 and providedwith ports 138 extending therethrough. The spacer 136 is formed with amedial portion 140 of increased diameter bounded at opposite ends byinwardly directed annular flanges or shoulders 142, 144. Seated on theseflanges 142, 144 are a pair of annular rings 146, 148 respectively, andthese rings or primary seals are constantly urged toward theirrespective seats by a spring .150 compressed therebetween within theannular area 140. In addition, annular sealing members 152, 154 aresecured to the opposite ends of the spacer 136, and these members areprovided with suitable or final seals 152', 154' respectively. Thus, thebearings 94 and 116 are both confined within areas sealed from theannular dust collection chamber 122.

While this sealing arrangement has been shown and described herein asbeing especially adapted for and utilized with a vacuum system whereinthe abrasive fines are evacuated from the annular area 140 through ports138, collection chamber 122 and port 130 by low pressure air, the sealarrangement is such that it is also effectively usable in a pressuresystem wherein a pressurized fluid, either air or water, is used to blowthe dust and cuttings away from the bit. In other words, pressurizedfluid may be supplied via pipe 132, and the flow through the chamber122, ports138, space 140, and passages 128, 124 and 126 is then reversedfrom that hereinabove described.

The drill steel chuck 14 is protectively sealed at its exposed forwardend by an annular seal 158 embracing and wiping over the reduced endportion 90 as the chuck 14 is operated. However, the sealing effect ofthe member 158 is preferably augmented by subjecting the areasurrounding the exposed end of the chuck to a ring of pressurized air.For this purpose, an annular groove 160 opening inwardly toward the seal158 and the adjacent end of the chuck 14 is formed in the housingportion 84, and this groove is placed in communication with a suitableexternal pressure source via passageway 162, 164 and hose 166. Thus, bysupplying pressurized air or the like to the annular groove 160, thearea entirely surrounding the seal 158 and end of the chuck is keptrelatively clean.

Returning now to the snubbing arrangement operative upon overtravel ofthe striker as hereinabove described, it should be noted that thehydraulic fluid in chamber 42 increases in pressure as the piston 40 isdeflected by the striker overtravel impact, such action being due to thefact that the ports 48 and 48" are sized to act as a variablerestriction to the hydraulic fluid being displaced from the chamber 42.Thus, as flange 46 of the snubber piston 40 is moved upon impact, itprogressively covers a portion of the ports 48, and while the annularpiston 40 initially moves at striker impact velocity, pressure buildupoccurs in chamber 42 commensurate with the velocity, piston area andorifice area to retard movement of the snubber, piston and striker 20.As the striker is thus slowed or retarded in its movement, the orificearea decrease should be such as to maintain essentially constantretarding pressure in the chamber 42, and the proper pressure may bemaintained as hereinabove described through use of a pressure regulatorand/or accumulator 54.

In order to return the piston 40 to its initial position, as shown inFIG. 1, after snubbing the striker 20, it is important that the pressureand the orifice area relationship be such as to return the pistongradually and over a time interval sufficient to reposition the same inreadiness for snubbing overtravel on the next stroke of the striker butwithout shock and creation of excessive stresses. Accordingly, in orderto reduce the velocity at which the snubbing piston 40 is returned toits initial position to thereby eliminate excessively high impactstresses, the snubber supply pressure annulus 48' should be inunrestricted communication with the port 48, and the entrance or mouthportion of the port 48 should preferably be formed with a radius so asto improve inflow of oil. In addition, it has been found preferable toundercut an annular area at the forward end of the chamber 42 as at 42for absorbing the initial pressure force for the start of therepositioning movement of the snubber piston, such arrangement beingmore clearly shown in the enlarged fragmentary sectional view of FIG. 3.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

We claim:

1. In a percussive drill, a housing having a bore, a drill steel chuckat one end of said housing in axial alignment with the bore thereof, astriker slidably mounted within the bore of said housing, means forreciprocating said striker to impart a succession of blows to saidchuck, an annular member surrounding said striker and independentlyslidable within predetermined limits in the bore of said housing and insealing engagement with said bore, said striker having a portioncooperable with one side of said annular member upon movement of saidstriker beyond its normal stroke in one direction, and fluid pressuremeans for constantly urging said annular member in the oppositedirection upon predetermined fluid pressure to cause said member toresist further movement of said striker in said one direction.

2. A percussive drill according to claim 1, wherein the annular memberis slidably confined in a separate annular chamber within the bore ofthe housing.

3. A percussive drill according to claim 2, wherein the annular chamberis pressurized by hydraulic fluid to constantly urge the annular memberin the direction causing said member to resist movement of the strikerbeyond its normal stroke, and means is provided for varying the pressurein said chamber and resistance to movement of said striker in responseto movement of said annular member.

4. A percussive drill according to claim 3, wherein a pressure regulatoris provided for controlling the pressure of the hydraulic fluid in theannular chamber.

5. A percussive drill according to claim 1, wherein the striker has anannular flange which forms the portion which is cooperable with one sideof the annular member upon the movement of the striker beyond its normalstroke.

6. A percussive drill according to claim 1, wherein a guide sleeve ishoused within the bore of the housing, and said guide sleeve hascylindrical portions cooperable with the striker and with the annularmember for guiding the same in their movement.

7. A percussive drill according to claim 6, wherein spring means betweenthe guide sleeve and the striker constantly urges said striker away fromthe chuck.

8. A percussive drill according to claim 7, wherein fluid under pressurebetween the guide sleeve and the annular member constantly urges saidannular member in a direction away from the chuck.

9. A percussive drill according to claim 6, wherein means is providedfor centering the guide sleeve within the bore of the housing and forabsorbing shock upon movement of the striker beyond its normal stroke.

10. A percussive drill according to claim 6, wherein the bore of thehousing is formed with an annular shoulder on which is seated aresilient ring and the guide sleeve is provided with an annular flangeseated against said resilient ring.

11. A percussive drill according to claim 10, wherein the annular flangeon the guide sleeve is tapered and the resilient ring is an O-ringcompressed between the shoulder of the bore and the tapered flange.

12. A percussive drill according to claim 6, wherein the bore of thehousing is formed with an annular shoulder on which is seated aresilient O-ring, the guide sleeve being formed with an annular taperedflange seated against said O- ring, and spring means is interposedbetween the guide sleeve and the striker for constantly urging saidstriker away from the chuck.

13. A percussive drill according to claim 1, wherein the chuck issurrounded by an annular chamber, and means is provided forcommunicating the chamber with a source of low pressure.

14. A percussive drill according to claim 13, wherein the chuck ismounted for both axial and rotational movement in bearings spaced atopposite ends of the annular chamber.

15. In a percussive drill, a housing having a bore, a drill steel chuckat one end of said housing in axial alignment with the bore thereof,means defining an annular space surrounding said chuck, means forimparting a succession of blows to said chuck for percussive operationthereof, means connecting the annular space with a source of vacuum toestablish and main tain a reduced pressure condition within the spaceand thereby remove dust therefrom, primary sealing rings surrounding thechuck at the opposite ends of the annular space, and spring meansinterposed between said primary sealing rings for constantly resilientlyurging said rings away from each other and toward seated condition.

16. A percussive drill according to claim 15, wherein the drill steelchuck is provided with a passageway constantly communicating the workingend of a drill steel carried thereby with the annular space surroundingthe chuck.

17. A percussive drill according to claim 16, wherein means is alsoprovided for rotating the chuck during the percussive operation thereof.

18. A percussive drill according to claim 15, wherein the chuck isrotatably mounted on bearings located beyond each of the primary sealingrings on the sides thereof remote from the annular space, and secondarysealing members are provided between each of the bearings and therespective primary sealing rings.

19. A percussive drill according to claim 15, wherein means are providedfor conducting pressurized fluid to the end of the housing entirelyaboutthe outer end of the drill steel chuck.

